Laparoscopic electrosurgical electrical leakage detection

ABSTRACT

An electrical leakage detection method and system for use with laparoscopic electrosurgical instruments are provided. The present disclosure provides for an electrosurgical unit for providing electrosurgical energy at an active output thereof and for controlling the flow of the energy through the active output; an active electrode coupled to the active output for transmitting electrosurgical energy to a patient in an electrosurgical procedure; a first sensor disposed at a distal end of the active electrode and for outputting a first signal indicative of current measured at the distal end; a second sensor disposed at a proximal end of the active electrode and for outputting a second signal indicative of current measured at the proximal end; and a comparison circuit coupled to the first and second sensors for receiving the first and second signals and determining a difference value, the difference value being indicative of leakage current.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present disclosure relates generally to electrosurgery andelectrosurgical systems and apparatuses, and more particularly, to anelectrical leakage detection method and system for use with laparoscopicelectrosurgical instruments.

2. Description of the Related Art

The term “laparoscope” comes from two Greek words. The first is lapara,which means “the soft parts of the body between the rib margins andhips”, or more simply, the “flank or lion”. The other Greek root isskopein, which means “to see or view or examine”. Skopein has becomescope in English. Therefore, a laparoscope is an instrument throughwhich structure within the abdomen and pelvis can be seen. A smallsurgical incision is made in the abdominal wall to permit thelaparoscope to enter the abdomen or pelvis. A diversity of tubes can bepushed through the same incision or other small incisions permitting theintroduction of probes and other instruments. In this way, a number ofsurgical procedures can be performed without the need for a largesurgical incision. Among the instruments used during a laparoscopicprocedure are electrosurgical instruments.

Laparoscopic surgery, a “minimally invasive” procedure, is commonly (butnot exclusively) used to treat diseases of the gastrointestinal tract.Unlike traditional surgery on the colon or other parts of the intestineswhere a long incision down the center of the abdomen is required,laparoscopic surgery requires only a small “keyhole” incision in theabdomen. As a result, the person undergoing the procedure may experienceless pain and scarring after surgery, and a more rapid recovery.

Electrosurgery is a term used to describe the passage of high-frequency(i.e., radio frequency) electrical current through tissue to create adesired clinical tissue effect. Through this technique, the targettissue, acting as a resistor in an electrical circuit, is heated by itsconduction of the electrical current. Electrocautery, as distinguishedfrom electrosurgery, uses an electrical current to heat a surgicalinstrument, which in turn conveys that heat to the target tissue.Electrosurgical electrode tips remain cool while targeted tissues heatup, primarily because the electrodes have much lower impedance than theadjacent targeted tissues. Electrosurgical tissue effects includecutting, coagulation, desiccation and fulguration. In addition, modernelectrosurgical generators can create blended modes of operation underwhich a surgeon can for example, cut and coagulate simultaneously.

In electrosurgery, there are two types of electrodes: mono-polar andbipolar. Mono-polar electrodes pass RF electrical current from anelectrosurgical generator through an active electrode into targetedtissue, through the patient, the dispersive electrode (e.g., a returnelectrode or pad), and back into the electrosurgical generator. If thereturn electrode is properly placed relative to the patient and surgicalsite, the electrosurgical tissue effects occur only at the activeelectrode and not the dispersive electrode. On the other hand, bipolarelectrodes are arranged in pairs (or poles, “+/−” and “−/+”) and formpart of the surgical instrument (e.g., electrosurgical forceps) withoutthe need for a separate return electrode (grounding) plate attached tothe patient. The intended flow of current is between the pair of bipolarelectrodes (from “+/−” to “−/+”), which are usually close together anduse relatively low voltage.

There are a number of well-known complications that may arise duringlaparoscopic electrosurgery. There are two major types of suchcomplications pertinent to this discussion. The first derive frominjuries caused by operator (i.e., surgeon) error such as directcoupling, perforation and laceration of targeted and non-targetedtissues. These injuries are outside the scope of this discussion. Thesecond group of complications occurs when targeted tissues get burnedfrom stray electricity emitting from or caused by other than operatorerror. There are two primary types of stray electricity applicable here.

The first type, insulation failure, involves faults in the insulation ofthe electrosurgical instrument—even a microscopic defect—that permitleakage of electrical current. The coating over metallic electrosurgicalinstruments intended to insulate then can be weakened by (i) repeatedinsertions into and removals from the patient, (ii) use of high voltage,(iii) material defects, and (iv) multiple sterilizations. A small holein the insulation can represent a higher risk of injury from straycurrent than a larger hole because of its concentrating effect on thecurrent density for such a leakage.

The second type of stray electricity results from capacitive coupling.Capacitive coupling occurs through instantaneous current inductionbetween instruments, or between an instrument and adjacent tissues. Thisphenomenon can occur even though the insulation is completely intact.Capacitive coupling requires a capacitor, which is created when twoconductors are separated by an insulator. The risk of this type of strayelectricity can increase when surgeons use disposable and reusableinstruments together during the same laparoscopic electrosurgicalprocedure.

The clinical complications from stray current caused by insulationfailure and capacity coupling are particularly challenging because theirinitial presentation often mimics normal post-surgical symptoms oflaparoscopy: namely, non-specific abdominal pain and slight to moderatefever. These clinical complications include perforation, blood vesseldamage, organ damage, and peritonitis. All of these, particularly fecalperitonitis, can lead to severe or fatal infection. Since injuriesresulting from stray current are most often undiscovered until daysafter surgery, and are often masked by unrelated conditions, preventionof these injuries cannot be overstressed.

SUMMARY OF THE INVENTION

An electrical leakage detection method and system for use withlaparoscopic electrosurgical instruments are provided. In particular,this disclosure concerns of the unique aspects of laparoscopicelectrosurgical electrical leakage detection and the prevention ofunintended injuries to non-targeted tissues.

In one aspect of the present disclosure, an electrosurgical apparatusfor use with an electrosurgical generator is provided including ahandpiece having a passage extending therethough, the hand piece havinga proximal end and a distal end; an active electrode having a tip andbeing adapted for coupling to said electrosurgical generator andextending through the passage for effecting at the tip thereof anelectrosurgical procedure; a first sensor disposed at the distal end ofthe handpiece and for outputting a first signal indicative of currentmeasured at the distal end; a second sensor disposed at the proximal endof the handpiece and for outputting a second signal indicative ofcurrent measured at the proximal end; and a differential device coupledto the first and second sensors for receiving the first and secondsignals and determining a difference value of the first and secondsignal, the difference value being indicative of leakage current.

In another aspect of the present disclosure, an electrosurgical systemfor controlling leakage during electrosurgical procedure is provided.The electrosurgical system includes an electrosurgical unit forproviding electrosurgical energy at an active output thereof and forcontrolling the flow of the energy through the active output, theelectrosurgical unit having a return input; an active electrode coupledto the active output for transmitting electrosurgical energy to apatient in an electrosurgical procedure; a return electrode adapted tobe coupled to the patient for receiving electrosurgical energy suppliedto the patient during the electrosurgical procedure and coupled to thereturn input for returning it to the return input of the electrosurgicalunit; a first sensor disposed at a distal end of the active electrodeand for outputting a first signal indicative of current measured at thedistal end; a second sensor disposed at a proximal end of the activeelectrode and for outputting a second signal indicative of currentmeasured at the proximal end; and a comparison circuit coupled to thefirst and second sensors for receiving the first and second signals anddetermining a difference value of the first and second signal, thedifference value being indicative of leakage current.

In a further aspect of the present disclosure, an endoscopic forceps foreffecting tissue includes an elongated shaft having opposing jaw membersat a distal end thereof, the jaw members being movable relative to oneanother from a first position wherein the jaw members are disposed inspaced relation relative to one another to a second position wherein thejaw members cooperate to grasp tissue therebetween; a handle assemblycoupled to a proximal end of the shaft for actuating the jaw membersbetween the first and second positions; each jaw member including anelectrically conductive surface and adapted to electrically couple to asource of electrical energy such that the jaw members are capable ofconducting energy to tissue held therebetween to effect anelectrosurgical procedure; a first sensor disposed at the distal end ofthe shaft and for outputting a first signal indicative of currentmeasured at the distal end; a second sensor disposed at the proximal endof the shaft and for outputting a second signal indicative of currentmeasured at the proximal end; and a differential device coupled to thefirst and second sensors for receiving the first and second signals anddetermining a difference value of the first and second signal, thedifference value being indicative of leakage current.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of the presentdisclosure will become more apparent in light of the following detaileddescription when taken in conjunction with the accompanying drawings inwhich:

FIG. 1 is an illustration of a laparoscopic electrosurgical system inaccordance with an embodiment of the present disclosure;

FIG. 2 is a flow diagram of a method for detecting leakage current in anelectrosurgical system in accordance with an embodiment of the presentdisclosure;

FIG. 3 is a block diagram of an electrosurgical generator andlaparoscopic instrument in accordance with an embodiment of the presentdisclosure;

FIG. 4 is a schematic diagram of a laparoscopic instrument for detectingleakage current in accordance with an embodiment of the presentdisclosure; and

FIG. 5A is a partial cross sectional view of an electrosurgical bipolarforceps in accordance with an embodiment of the present disclosure;

FIG. 5B illustrates an end effector assembly of the bipolar forcepsshown in FIG. 5A in an open position; and

FIG. 5C is a schematic diagram of a current sensor in accordance withthe present disclosure.

DETAILED DESCRIPTION

Preferred embodiments of the present disclosure will be describedhereinbelow with reference to the accompanying drawings. In thefollowing description, well-known functions or constructions are notdescribed in detail to avoid obscuring the present disclosure inunnecessary detail. In the drawings and in the description which follow,the term “proximal”, as is traditional, will refer to the end of thedevice, e.g., instrument, handpiece, forceps, etc., which is closer tothe user, while the term “distal” will refer to the end which is furtherfrom the user. Herein, the phrase “coupled” is defined to mean directlyconnected to or indirectly connected with through one or moreintermediate components. Such intermediate components may include bothhardware and software based components.

An electrical leakage detection method and system for use withlaparoscopic electrosurgical instruments are provided. The techniques ofthe present disclosure provide for: (a) detecting the occurrence of anelectrical leakage event (e.g., stray electrical current) duringlaparoscopic electrosurgery, (b) instantly shutting down theelectrosurgical generator to prevent stray electrical current injury tothe patient, and (c) warning the operator of an electrical leakageincident. Some in the field have used multiple layers of insulation inan attempt to avoid the electrical leakage problem caused by insulationfailure; however, this approach, even if fully effective, does notaddress the capacitive coupling problem. Others have employed methods todetect a loss of contact between the patient and the grounding pad usedin mono-polar electrosurgery. Still others have used methods that relayon measurements within the electrosurgical generator, and not in or nearthe electrosurgical instruments themselves. However, such measures donot adequately address the specific problem of electrical leakage fromlaparoscopic electrosurgical instruments.

Rather than employing such approaches, the system and method of thepresent disclosure seeks to measure the electrical current at two keypoints along the path of electrosurgical current created by theelectrosurgical generator, the power cord connecting the laparoscopicinstrument body, the laparoscopic instrument body, and the electrodetip.

Referring to FIG. 1, an electrosurgical system 10 is shown including anelectrosurgical generator (ESU) 12 and a larascopic instrument 14. Theelectrosurgical generator 12 is configured for supplying electrosurgicalenergy via a laparoscopic instrument 14 to an operative site of apatient, e.g., tissue. The electrosurgical laparoscopic apparatus 14includes a trocar sheath or cannula 16 which is conventionally used toprovide a conduit through a patient's skin into the peritoneal cavity.Removably insertable through the trocar sheath is an active electrodeprobe or handpiece 18 which includes an active electrode 20 disposedwithin a passage of the handpiece and an insulative coating 22 thereon.The distal end of the electrode 20 includes a tip 24 for affecting asurgical procedure at the operative site. The tip 24 of the probe may beof different conventional shapes such as needle-shape, hook-shape,spatula-shape, graspers, scissors, etc. and serve various conventionalfunctions such as suction, coagulation, irrigation, pressurized gas,cutting, etc. Furthermore, the instrument 14 is coupled to the generator12 via a power cord cable 25.

In FIG. 1, the first test point is at or very near the electrode tip 24(Location “A”), e.g., a distal end of the instrument 14. The second testpoint is at the connection power cord's entry point into thelaparoscopic instrument or just before it (Location “B”), e.g., aproximal end of the instrument 14. Then, by comparing the measuredcurrent at these two test points “A” and “B”, the electrosurgicalgenerator 12 can determine if there is a drop in output current,impliedly indicating electrical leakage. Conventional electrosurgicalgenerator systems are capable of measuring output voltage (and otherelectrosurgical parameters such as tissue impedance) at the rate of 5KHz. Given that very high rate, an automated decision to shut down thegenerator could occur very rapidly—virtually instantaneously—and therebyprotect the patient from stray electrical current.

It is to be appreciated that the measurements taken at points “A” and“B” can be measured by a sensor 26 disposed adjacent the distal end ofinstrument 14 and sensor 28 disposed adjacent the proximal end of theinstrument 14. As will be described below, the sensors 26, 28 mayinclude a current sensor, resistor, or the like. The sensors 26, 28 willtransmit the measured values to the electrosurgical generator 12 viahardwire or wireless means. In one embodiment, conductors carrying themeasured values at Locations A and B are disposed in cable 25. In afurther embodiment, the sensors 26, 28 will transmit the measured valuesvia an RF signal to a receiver disposed in the electrosurgical generator12.

In a further embodiment, the instrument 14 will include a differentialdevice, e.g., a comparator, differential amplifier, etc., thatdetermines the difference value and transmits a single difference valueto the electrosurgical generator 12.

It is further to be appreciated that the second test point may bemeasured at the electrosurgical generator 12 (Location “C”). In thisembodiment, the sensor is disposed in the electrosurgical generator 12and measured the current leaving the generator 12. The leakage currentis then determined by calculating the difference between the currentmeasured at Location A and Location C. In this embodiment, only sensor26 is disposed in the instrument 14 resulting in a lower costinstrument.

Referring to FIG. 2, a method for detecting leakage current in anelectrosurgical system is illustrated. Initially, at step 50, current isdetermined at the electrode tip 24, i.e., Location A. Next, the currententering the instrument, i.e., Location B, is determined in step 52. Itis to be appreciated that in certain embodiments the current enteringthe instrument will be measured as current leaving the electrosurgicalgenerator 12, i.e., Location C. Next, in step 54, a difference in thecurrent measured at Locations A and B is determined.

In step 56, it is determined if the difference is greater than apredetermined threshold. If the difference is less than thepredetermined threshold, no leakage current has been detected, or anacceptable amount of leakage current has been detected, and the methodwill revert to step 50 to continue to monitor the current at Locations Aand B. If the difference is greater than the predetermined threshold,leakage current has been detected. When leakage current has beendetected, the RF output from the electrosurgical generator 12 will beterminated in step 58. Furthermore, in step 60, the electrical leakagecondition will be indicated to the operator, e.g., a surgeon, via theelectrosurgical generator 12 or laparoscopic instrument 14. It is to beappreciated that steps 58 and 60 may be performed simultaneously and/orstep 60 may be performed before step 58.

Alternative embodiments for the system of the present disclosure will bedescribed below. The various embodiments focus on the technique ofmeasuring voltage, calculating current, and comparing those valuesbetween Locations “A” and “B”, as described above.

Referring to FIG. 3, one embodiment of the system contemplates placementof a series resistor (R_(A)) at Location ‘A’ in instrument 114. UsingOhm's Law (i.e., V=IR, where V is voltage, I is current, and R isresistance), the current I_(A) for a measured voltage V_(A) can becalculated. Thus, I_(A)=V_(A)/R_(A). The challenge with this design isthe need to transfer the calculated value of current at Location A(I_(A)) back to the generator. One solution is to place means ofconverting I_(A) from an analog to a digital value, which can then betransmitted back to the generator, free from electrical or magneticinterference. In one embodiment, an analog to digital converter ADC 126may be coupled to resistor R_(A) for transmitting the measured voltageacross resistor R_(A) to electrosurgical generator 112. The digitalsignal will be sent to a controller 130, e.g., a microprocessor, whichcan determine a current value from the measured voltage. Thus, byconverting the value to the digital domain, rapid and accuratemonitoring of current can be maintained. The same technique could beemployed at Location B with a second series resistor R_(B) and secondADC 128. As described above, the measured values may be transmitted tothe generator 112 via conductors or other known transmission means incable 125, or alternatively, may be bundled in a second cable separatefrom the power cable 125. If a leakage condition is detected, thecontroller 130 will control the HV DC power supply 132 to terminate theelectrosurgical energy being output from the RF output stage 134.Furthermore, as described above, the electrosurgical generator 112 willindicate the condition to an operator via an I/O interface 136 such as atouch screen or an audible alarm 138.

In a further embodiment, the electrosurgical generator 112 includes acomparison circuit 142 that receives the signals from the sensorsdisposed in the instrument 114. The comparison circuit 142 determinesthe difference between the received signals and transmits a singledifference value to the controller 130. The controller 130 thendetermines if the difference value is greater than a predeterminedthreshold. If so, the controller 130 will terminate the output ofelectrosurgical energy by controlling the HV DC power supply 132.

It is expected that each combination of generator 112 and connectingpower cord 125 to the instruments 114 will exhibit some inherentresistance. Accordingly, there will be a correction factor for thatcombination stored in a memory 140 of the generator 112. Differencesbetween calculated current values at Locations A and B, adjusted by thecorrection factor, indicate a loss of current suggesting electricalleakage. Based on preset thresholds, the generator 112 can detect athreshold difference, set an alarm and shut down the generator. In thisway, the patient can be protected from unintended injury (e.g., burns)from stray current.

In another embodiment, a dual current sensing transformer arrangement,both with the same turns ratio, is used in combination with means forconverting analog measurements to digital values, as shown in FIG. 4. Inthis embodiment, a first distal coil L1 can be constructed from theconductor material itself within the instrument body at a distal end202. A second proximal coil L2 is then formed and placed at a proximalend 204 of the instrument. The induced current in the coil L1 isconverted to voltage V1 via resistor R1 and capacitor C1 which arecoupled in parallel. Similarly, induced current in coil L2 is convertedto voltage V2 via resistor R2 and capacitor C2. The difference betweenvoltage V1 (indicative of the current induced in the distal coil L1) andvoltage V2 (indicative of the current induced in the proximal coil L2)can then be measured, digitized and transmitted back to the generatorvia analog-to-digital converter ADC 206. By using two identicaltransformers and passing high current through them, the system of thepresent disclosure can achieve improved noise immunity and measurementaccuracy.

Another embodiment according to the present disclosure includes amonopolar forceps for affecting tissue having an elongated shaft withopposing jaw members at a distal end thereof. The jaw members aremovable relative to one another from a first position wherein the jawmembers are disposed in spaced relation relative to one another to asecond position wherein the jaw members cooperate to grasp tissuetherebetween. By utilizing an electrosurgical forceps, a surgeon caneither cauterize, coagulate/desiccate and/or simply reduce or slowbleeding, by controlling the intensity, frequency and duration of theelectrosurgical energy applied through the jaw members to the tissue.The electrode of each jaw member is charged to the same electricpotential such that when the jaw members grasp tissue, electrical energycan be selectively transferred to the tissue.

Referring to FIG. 5, one embodiment of a monopolar forceps 300 is shownfor use with various surgical procedures and generally includes ahousing 302, a handle assembly 304, a trigger assembly 306 and an endeffector assembly 308 which mutually cooperate to grasp, seal and dividetubular vessels and vascular tissue. More particularly, forceps 300includes a shaft 310 which has a distal end 312 dimensioned tomechanically engage the end effector assembly 308 and a proximal end 314which mechanically engages the housing 302.

Forceps 300 also includes an electrical interface or plug 316 whichcouples the forceps 300 to a source of electrosurgical energy, e.g., agenerator. Plug 316 includes a pair of prong members 318 which aredimensioned to mechanically and electrically couple the forceps 300 tothe source of electrosurgical energy. An electrical cable 320 extendsfrom the plug 316 to the forceps 300. Cable 320 is coupled to conductor334 which extends along the shaft and is further coupled to theconducting surfaces of the end effector assembly 308.

Handle assembly 304 includes a fixed handle 322 and a movable handle324. Fixed handle 322 is integrally associated with housing 302 andhandle 324 is movable relative to fixed handle 322 to effect operationof the forceps 300.

As mentioned above, end effector assembly 308 is attached to the distalend 312 of shaft 310 and includes a pair of opposing jaw members 326 and328. Movable handle 324 of handle assembly 304 is ultimately coupled toan actuation assembly (not shown) which, together, mechanicallycooperate to impart movement of the jaw members 326 and 328 from an openposition wherein the jaw members 326 and 328 are disposed in spacedrelation relative to one another, to a clamping or closed positionwherein the jaw members 326 and 328 cooperate to grasp tissuetherebetween. Once the tissue is grasped, electrosurgical energy will beapplied in response to trigger 306 or a footswitch coupled to thegenerator.

As mentioned above, the cable lead extend through the shaft 310conducting electrosurgical energy from the generator to the jaw members326, 328 of the end effector assembly 308. As illustrated in FIG. 5B,each jaw member 326, 328 includes an internal conducting surface 330,332 respectively for contacting tissue therebetween. In one embodiment,the cable 334 is coupled to and supplies electrosurgical energy to thetwo conducting surfaces 330, 332. In this manner, the conductingsurfaces 330, 332 are the active electrode and a return electrode, e.g.,a return pad, is coupled to the patient for returning electrosurgicalenergy to the generator.

Referring back to FIG. 5A, a first current sensor 336, i.e., distalcurrent sensing transformer, is disposed around the cable 334, i.e., theactive electrode conductor, adjacent the distal end 312 of the shaft310. A second current sensor 338, i.e., proximal current sensingtransformer, is disposed around the cable 334 adjacent the proximal end314 of the shaft 310. Referring to FIG. 5C, the first and second currentsensors 336, 338 include a capacitor Cn, a resistor Rn and a toroidal orhollow cylindrical core inductor Ln. It is to be appreciated thecapacitor Cn, resistor Rn and inductor Ln will be disposed in thehousing 302. The first and second current sensors 336, 338 will operatein cooperation to determine the difference in current, i.e., leakagecurrent, between the distal end of the instrument and proximal end inaccordance with the various embodiments described above.

It is envisioned that the forceps 300 may be designed such that it isfully or partially disposable depending upon a particular purpose or toachieve a particular result. For example, end effector assembly 308 maybe selectively and releasably engageable with the distal end 312 of theshaft 310 and/or the proximal end 314 of shaft 310 may be selectivelyand releasably engageable with the housing 302 and the handle assembly304. In either of these two instances, the forceps 300 would beconsidered “partially disposable” or “reposable”, i.e., a new ordifferent end effector assembly 308 (or end effector assembly 308 andshaft 310) selectively replaces the old end effector assembly 308 asneeded.

In a further embodiment, the instrument shown in FIG. 5A will beconfigured as bipolar forceps. Although not shown, in the bipolarembodiment, cable 320 is internally divided into two cable leads, e.g.,first and second cable leads, which transmit electrosurgical energythrough their respective feed paths through the forceps 300 to the endeffector assembly 308. Here, the electrode of each jaw member is chargedto a different electric potential such that when the jaw members grasptissue, electrical energy can be selectively transferred through thetissue.

In the bipolar embodiment, the first and second cable leads extendthrough the shaft 310 conducting electrosurgical energy from thegenerator to the jaw members 326, 328 of the end effector assembly 308.Similar to the embodiment described above in relation to FIG. 5B, eachjaw member 326, 328 includes an internal conducting surface 330, 332respectively for contacting tissue therebetween. The first cable 334 iscoupled to and supplies electrosurgical energy to conducting surface 330while the second cable (not shown) is coupled to conducting surface 332and returns the electrosurgical energy to the generator. In this manner,the conducting surface 330 is the active electrode and the conductingsurface 332 is the return electrode, i.e., no additional return pad isnecessary.

In the bipolar embodiment, a first current sensor 336 is disposed aroundthe cable 334, i.e., the active electrode conductor, adjacent the distalend 312 of the shaft 310 and a second current sensor 338 is disposedaround the cable 334 adjacent the proximal end 314 of the shaft 310,similar to the embodiment described above in relation to the monopolarembodiment. The first and second current sensors 336, 338 are configuredas shown in FIGS. 5A and C. The first and second current sensors 336,338 will operate in cooperation to determine the difference in current,i.e., leakage current, between the distal end of the instrument andproximal end in accordance with the various embodiments described above.

While the disclosure has been shown and described with reference tocertain preferred embodiments thereof, it will be understood by thoseskilled in the art that various changes in form and detail may be madetherein without departing from the spirit and scope of the disclosure asdefined by the appended claims.

Furthermore, although the foregoing text sets forth a detaileddescription of numerous embodiments, it should be understood that thelegal scope of the invention is defined by the words of the claims setforth at the end of this patent. The detailed description is to beconstrued as exemplary only and does not describe every possibleembodiment, as describing every possible embodiment would beimpractical, if not impossible. One could implement numerous alternateembodiments, using either current technology or technology developedafter the filing date of this patent, which would still fall within thescope of the claims.

It should also be understood that, unless a term is expressly defined inthis patent using the sentence “As used herein, the term ‘_(——————)’ ishereby defined to mean . . . ” or a similar sentence, there is no intentto limit the meaning of that term, either expressly or by implication,beyond its plain or ordinary meaning, and such term should not beinterpreted to be limited in scope based on any statement made in anysection of this patent (other than the language of the claims). To theextent that any term recited in the claims at the end of this patent isreferred to in this patent in a manner consistent with a single meaning,that is done for sake of clarity only so as to not confuse the reader,and it is not intended that such claim term be limited, by implicationor otherwise, to that single meaning. Finally, unless a claim element isdefined by reciting the word “means” and a function without the recitalof any structure, it is not intended that the scope of any claim elementbe interpreted based on the application of 35 U.S.C. §112, sixthparagraph.

1. An electrosurgical apparatus for use with an electrosurgicalgenerator comprising: a handpiece having a passage extendingtherethough, the hand piece having a proximal end and a distal end; anactive electrode having a tip and being adapted for coupling to saidelectrosurgical generator and extending through the passage foreffecting at the tip thereof an electrosurgical procedure; a firstsensor disposed within the distal end of the handpiece and foroutputting a first signal indicative of current measured at the distalend of the active electrode; a second sensor disposed within theproximal end of the handpiece and for outputting a second signalindicative of current measured at the proximal end of the activeelectrode; and a differential device coupled to the first and secondsensors for receiving the first and second signals and determining adifference value of the first and second signal, the difference valuebeing indicative of leakage of current within the handpiece.
 2. Theelectrosurgical apparatus of claim 1, wherein each of the first andsecond sensors is a resistor in series with the active electrode.
 3. Theelectrosurgical apparatus of claim 2, further comprising an analog todigital converter coupled to each resistor.
 4. The electrosurgicalapparatus of claim 1, wherein each of the first and second sensors is acurrent sensor.
 5. The electrosurgical apparatus of claim 1, whereineach of the first and second sensors is a transformer.
 6. Theelectrosurgical apparatus of claim 5, wherein each transformer includesa core disposed around the active electrode, wherein the activeelectrode passes therethrough.
 7. The electrosurgical apparatus of claim1, wherein the first and second sensors are configured as a singletransformer, the first sensor being configured as a first coil disposedadjacent the distal end of the handpiece and the second sensor beingconfigured as a second coil disposed adjacent the proximal end of thehandpiece.
 8. An electrosurgical system for controlling leakage duringelectrosurgical procedure comprising: an electrosurgical unit forproviding electrosurgical energy at an active output thereof and forcontrolling the flow of the energy through the active output, theelectrosurgical unit having a return input; an active electrode coupledto the active output for transmitting electrosurgical energy to apatient in an electrosurgical procedure; a handpiece for supporting theactive electrode; a return electrode adapted to be coupled to thepatient for receiving electrosurgical energy supplied to the patientduring the electrosurgical procedure and coupled to the return input forreturning it to the return input of the electrosurgical unit; a firstsensor disposed at a distal end of the active electrode within thehandpiece and for outputting a first signal indicative of currentmeasured at the distal end of the active electrode; a second sensordisposed at a proximal end of the active electrode within the handpieceand for outputting a second signal indicative of current measured at theproximal end of the active electrode; and a comparison circuit coupledto the first and second sensors for receiving the first and secondsignals and determining a difference value of the first and secondsignal, the difference value being indicative of leakage of currentwithin the handpiece.
 9. The electrosurgical system of claim 8, furthercomprising a controller for controlling the output of electrosurgicalenergy and coupled to the comparison circuit for receiving thedifference value, wherein if the difference value is greater than apredetermined threshold, the controller terminates the output ofelectrosurgical energy.
 10. The electrosurgical system of claim 8,wherein the comparison circuit is disposed in the handpiece.
 11. Theelectrosurgical system of claim 8, wherein the comparison circuit isdisposed in the electrosurgical unit.
 12. The electrosurgical system ofclaim 8, wherein each of the first and second sensors is a resistor inseries with the active electrode.
 13. The electrosurgical system ofclaim 8, wherein each of the first and second sensors is a currentsensor.
 14. The electrosurgical system of claim 8, wherein each of thefirst and second sensors is a transformer.
 15. The electrosurgicalsystem of claim 8, wherein the first and second sensors are configuredas a single transformer, the first sensor being configured as a firstcoil disposed adjacent the distal end of the handpiece and the secondsensor being configured as a second coil disposed adjacent the proximalend of the handpiece.
 16. The electrosurgical system of claim 8, furthercomprising an indicator device for indicating to an operator when thedifference value is greater than a predetermined threshold.
 17. Anendoscopic forceps for effecting tissue, comprising: an elongated shafthaving opposing jaw members at a distal end thereof, the jaw membersbeing movable relative to one another from a first position wherein thejaw members are disposed in spaced relation relative to one another to asecond position wherein the jaw members cooperate to grasp tissuetherebetween; a handle assembly coupled to a proximal end of the shaftfor actuating the jaw members between the first and second positions;each jaw member including an electrically conductive surface and adaptedto electrically couple to a source of electrical energy such that thejaw members are capable of conducting energy to tissue held therebetweento effect an electrosurgical procedure; a first sensor disposed withinthe distal end of the shaft and for outputting a first signal indicativeof current measured at the distal end of the shaft; a second sensordisposed within the proximal end of the shaft and for outputting asecond signal indicative of current measured at the proximal end of theshaft; and a differential device coupled to the first and second sensorsfor receiving the first and second signals and determining a differencevalue of the first and second signal, the difference value beingindicative of leakage of current within the shaft.
 18. The endoscopicforceps of claim 17, wherein each of the first and second sensors is atransformer including a core disposed around a conductor supplyingelectrosurgical energy to at least one conductive surface of at leastone jaw member, wherein the conductor passes through each core.